Turbine Operation Research Articles

U susret revitalizaciji turbina HE Đerdap 2: Merenje rasporeda vektora brzina na ulazima turbina

The continuous flow measurement on hydroelectric turbine units is conventionally carried out using the relative methods (mostly Winter-Kennedy), where the complex velocity field in flow cross section is replaced by a single measured quantity. On a physical model, mapping parameters are determined. The Winter-Kennedy method is most used, where this relative (index) flow quantity is obtained by measuring differential pressure. The measurement uncertainty of the determined flow using this method is usually significantly higher than the uncertainty of other relevant quantities for determining the optimal turbine operating conditions. To reduce the flow uncertainty, it is necessary to perform "absolute measurements" of the entire velocity field and determine the necessary corrections to the index method under real operating conditions. This is especially true for plants where disposition is different from one used on physical model, which is the case of “Đerdap 2” and recognized problem of skewed inflow. With the aim of better assessing the hydraulic efficiency of turbines and to collect data on the actual operating velocity distribution in the inlet section in front of trash-rack needed for planned revitalization works, an innovative system for absolute flow measurement has been designed and implemented. The moving frame was designed and installed at the turbine inlet, upstream from the trash-rack. The 15 electromagnetic (EM) sensors and two redundant acoustic Doppler sensors were installed on horizontal bar. Each sensor measures all three velocity components. The frame moves by lifting along the entire height of the flow section, allowing the entire velocity field to be scanned. The position of the frame is tracked by two encoders, while two pressure sensors are used to measure the water depth. Measurements are synchronized with the local SCADA system, so appropriate turbine operation data are also used. Considering the specificities of the measurement system itself with newly developed EM sensors, as well as hydraulic conditions, an adequate procedure has been developed to assess the uncertainty of the measured flow. This paper presents the measurement method and provides some measurement results on the units of the “Đerdap 2” hydroelectric power plant.

A Methodology for Designing a Fish-Friendly Turbine Rotor Applied to High-Power Generation

Most large hydropower facilities employing conventional hydraulic turbines, e.g., Francis, Kaplan, or Bulb turbines, etc., cause significant harm to fish, resulting in high mortality rates, during turbine operation. This results from strong injury-inducing mechanisms at the rotor, including shear stresses, pressure variations, and pressure drop through the rotor. The study outlines a methodology for designing a fish-friendly turbine that is suitable for high-power generation applications. This methodology for a hydraulic channel design within the turbine rotor was derived based on classical fundamental applications of a rotor design, supplemented by subsequent assessments that incorporate fish-friendly design parameters that have been documented in the existing literature. A spiral curve characterized by a linear angle variation between the rotor's inlet and outlet was employed to project the blade geometry. Here, the Göttingen hydrofoil series was used, while a second-order polynomial function guided the hub design. Both of these parametrizations sought to enhance the turbine's hydraulic efficiency. Minimum Absolute Pressure, Strain Rate, and Pressure Variation Rate intervals were established as assessment criteria for fish survival for certain species, as has also been previously explored in the literature. The findings were outlined in terms of hydrodynamic performance and flow behavior within the rotor. An improvement in hydraulic efficiency was observed, transitioning from a Preliminary Turbine geometry design to an Optimized Turbine Geometry design. The turbine rotor was optimized using Computational Fluid Dynamics (CFD) simulations, generated from a Design of Experiments (DOE). Modifications to the hydrofoil type, the sweep angle, and the trailing edge angle of the blades were all made, coupled with integrations of assessments considering fish-friendly parameters.

Open channel velocity field investigation for hydrokinetic power generation

The paper presents an experimental study of a velocity field in an open channel. The study of water flow in an open channel is complicated due to the influence of various factors and different variables. Some of the variables affecting the flow parameters include the height of the water column, the width of the channel, the length of the channel, the slope of the channel, and the conditions of the channel bed. The investigated open channel is used for experimental research of kinetic turbines, and the flow speed in the channel is in the range of 0.1-0.3 m/s. The low velocity values in the channel are driven by the operation of the kinetic water turbines in real-world conditions. When describing the test channel, the influence of several boundary conditions has been taken into account, such as protrusions between the measurement sections, the water level, and disturbing effects. Results for the velocity fields determined in five sections of the test open channel are given. A turbine and an electromagnetic probe were used for the experiments. A comparison between the results obtained with the two measuring instruments under the same flow conditions in the test channel is made. The results for the velocity variation in the test sections for the maximum velocity in the channel are presented. At this maximum water velocity, the test channel maintains a water level of approximately 150 mm. The experimental data is also illustrated graphically, along with the velocity fluctuations along the channel centreline. The results obtained provide an idea of the expected velocity fields in the measurement open channel and the relative magnitude of the fluctuations in the different measurement sections.

A Drone-Driven X-Ray Image-Based Diagnosis of Wind Turbine Blades for Reliable Operation of Wind Turbine

A Drone-Driven X-Ray Image-Based Diagnosis of Wind Turbine Blades for Reliable Operation of Wind Turbine

Use of the heat of exhaust fluge gases of gas turbine units in recovery boilers for heat and electric supply systems

In this article, the inextricable interconnection and interdependence of the conditions for ensuring the heat of energy consumption is considered. A highly efficient installation covers the heat and energy needs of the Mubarek gas processing plant. With simultaneous operation of gas turbine and steam boiler plant efficiency reaches 95%. The introduction of the proposed development will solve the problem of energy and resource-saving, enables the use of a steam boiler in heat supply and solves an environmental problem.

Surface kinetics and pressure dependence of propane oxidation over platinum

The catalytic total oxidation of propane over platinum was investigated experimentally and numerically at pressures of 1–7 bar and catalyst temperatures up to 700 K. A wire microcalorimeter was employed to determine the global rate parameters of the catalytic reaction within the kinetically controlled regime. For 1 bar pressure, the dissociative adsorption of C3H8 on Pt and its subsequent decomposition were modeled as two lumped steps based on global reaction parameters. A detailed and thermodynamically consistent catalytic mechanism was constructed by incorporating these lumped steps with an existing atmospheric-pressure H-C2 elementary reaction model. Two-dimensional CFD simulations using the developed global and detailed reaction mechanisms closely reproduced the measured heat release rates. The intricate dependence of catalytic ignition and reactivity on pressure was further elucidated. Ignition temperatures were found to be linearly correlated to pressures, due to the weaker net adsorption of oxygen compared to that of propane, which progressively aggravated at higher pressures and in turn hindered ignition. More importantly, a non-monotonic pressure dependence of the C3H8 catalytic reactivity on Pt, which gradually diminishes with increasing temperatures, is reported for the first time. The temperature range of this non-monotonic behavior (< 650 K) is of special importance for part-load and idling operations of gas turbines using hybrid hetero-/homogeneous combustion approaches and for normal operations of recuperative microreactors. Thus, this work provides key information for the design and optimization of such devices utilizing Pt as catalyst.

Application of advanced signal processing techniques in vibration analysis and fault diagnosis of multi-dimensional anthropomorphic wind turbines

Abstract Wind turbine operating conditions are complex. To ensure the turbine’s safe operation, it is essential to carry out condition monitoring and fault diagnosis of its vibration. In this paper, from the structure of wind turbines, fault types, and fault formation mechanisms, a wind turbine vibration condition monitoring system is established by designing different vibration condition monitoring sensors and combining them with the Internet of Things technology. The discrete Fourier transform is employed to preprocess the time-frequency data before extracting the specific features of the vibration signal by combining the Hilbert-Huang transform after obtaining the wind turbine vibration signal. The SC-TSFN model with spatio-temporal deep fusion is established to realize the fault diagnosis of wind turbines by combining the replaceable null convolution module, BiLSTM module and the self-attention mechanism. It has been found that when the tertiary meshing frequency fluctuates around 506.98 Hz at a fault characteristic frequency of 16.14 Hz, it indicates a fault in the tertiary high-speed shaft gear. The SC-TSFN model has a fault identification time of approximately 52 days before the actual fault downtime, and the model has a 92.05% accuracy rate for wind turbine fault identification. Relying on the signal processing technology to carry out the wind turbine vibration signal analysis and then input it into the fault identification model can realize the accurate identification of the fault state of the unit and provide technical support for the stable operation of wind turbines.

Modern Strategies for Controlling Wind Power Plants: Technologies, Challenges and Prospects

This paper explores the evolution of wind power plant (WPP) control strategies, from simple approaches aimed at optimizing the operation of individual wind turbines to the development of more complex systems that manage WPPs as single integrated entities. Particular attention is paid to the key requirements for WPP control systems and the analysis of WPP structure, especially in the context of their integration into the overall power system. The main objectives of WPP control systems have been studied. The paper presents a detailed review and analysis of the control strategies that are being actively investigated. The control strategies that have successfully found commercial application are identified, and directions for further research needed to optimize and improve these strategies are outlined.

Research of influencing factors on tripping speed of double plungers turbine overspeed protector

The over-speed protection mechanism is very important for the safe operation of the steam turbine, but in actual production, the tripping speed often fluctuates and deviates from the set value, resulting in a decrease in the reliability of the unit operation. In this paper, the factors that affect the tripping speed of double plungers turbine overspeed protection mechanism are analysed, the mechanism of mechanical vibration and friction that cause the tripping speed to fluctuate is explored through theoretical calculation and simulation analysis, and the change of spring dynamic stiffness by using the dynamic stiffness matrix method and finite element simulation is analysed. The change of friction force under different contact modes is calculated by using the L-N contact force model and the modified Coulomb friction model, and the change of tripping speed under non-ideal friction conditions is explored through dynamic simulation.

Given-data probabilistic fatigue assessment for offshore wind turbines using Bayesian quadrature

Abstract Offshore wind turbines intend to take a rapidly growing share in the electric mix. The design, installation, and exploitation of these industrial assets are regulated by international standards, providing generic guidelines. Constantly, new projects reach unexploited wind resources, pushing back installation limits. Therefore, turbines are increasingly subject to uncertain environmental conditions, making long-term investment decisions riskier (at the design or end-of-life stage). Fortunately, numerical models of wind turbines enable to perform accurate multi-physics simulations of such systems when interacting with their environment. The challenge is then to propagate the input environmental uncertainties through these models and to analyze the distribution of output variables of interest. Since each call of such a numerical model can be costly, the estimation of statistical output quantities of interest (e.g., the mean value, the variance) has to be done with a restricted number of simulations. To do so, the present paper uses the kernel herding method as a sampling technique to perform Bayesian quadrature and estimate the fatigue damage. It is known from the literature that this method guarantees fast and accurate convergence together with providing relevant properties regarding subsampling and parallelization. Here, one numerically strengthens this fact by applying it to a real use case of an offshore wind turbine operating in Teesside, UK. Numerical comparison with crude and quasi-Monte Carlo sampling demonstrates the benefits one can expect from such a method. Finally, a new Python package has been developed and documented to provide quick open access to this uncertainty propagation method.

On the Low Risk of SSR in Type III Wind Turbines Operating With Grid-Forming Control

On the Low Risk of SSR in Type III Wind Turbines Operating With Grid-Forming Control

Numerical study of the effect of NH3 addition on CH4/air combustion characteristics under gas turbine operating conditions

In this study, the effects of different NH3 additions on the laminar premix combustion characteristics of CH4/air flame were investigated, including laminar combustion velocity, ignition delay time, four important free radicals and NO emission.

Wind Turbine Geometrical and Operation Variables Reconstruction from Blade Acceleration Measurements

To develop reliable numerical models and better interpret monitoring campaigns experimental data of wind turbines, knowing the structure operation conditions, in particular the rotor angular velocity and blades’ pitch angle, is of paramount importance, but often not known due to confidentiality restrictions, or known with low time resolution (typically 10 min average values). In this work, it is shown analytically that blades accelerations measurements contain valuable information that allow for a better characterisation of the effective rotor shaft tilt and blades cone angle for different operating conditions. It is also shown that these measurements can be used to reconstruct the time history of the rotor angular velocity and blades’ pitch angle. After presented in an analytical framework, the methodology is validated with experimental data of two full scale wind turbines. The successful reconstruction of the rotor operating conditions shows that the method presented can be used to provide further insight into the dynamics of the structure that aids monitoring data analysis and provides an alternative method to monitor the SCADA systems themselves. The paper combines quite unique experimental data collected at two operating rotors with original data processing strategies that provide very valuable information to researchers and wind turbine operators.

Damage Detection and Localization at the Jacket Support of an Offshore Wind Turbine Using Transformer Models

Early detection of damage in the support structure (submerged part) of an offshore wind turbine is crucial as it can help to prevent emergency shutdowns and extend the lifespan of the turbine. To this end, a promising proof-of-concept is stated, based on a transformer network, for the detection and localization of damage at the jacket-type support of an offshore wind turbine. To the best of the authors’ knowledge, this is the first time transformer-based models have been used for offshore wind turbine structural health monitoring. The proposed strategy employs a transformer-based framework for learning multivariate time series representation. The framework is based on the transformer architecture, which is a neural network architecture that has been shown to be highly effective for natural language processing tasks. A down-scaled laboratory model of an offshore wind turbine that simulates the different regions of operation of the wind turbine is employed to develop and validate the proposed methodology. The vibration signals collected from 8 accelerometers are used to analyze the dynamic behavior of the structure. The results obtained show a significant improvement compared to other approaches previously proposed in the literature. In particular, the stated methodology achieves an accuracy of 99.96% with an average training time of only 6.13 minutes due to the high parallelizability of the transformer network. In fact, as it is computationally highly efficient, it has the potential to be a useful tool for implementation in real-time monitoring systems.

Sewage sludge co-pyrolysis with agricultural/forest residues: A comparative life-cycle assessment

This study aims to determine the sustainability and energy efficiency of co-pyrolysis scenarios as treatment processes for municipal sewage sludge through a life cycle assessment (LCA). In addition, sensitivity and energy recovery analyses are conducted to determine the possible methods for optimizing the co-pyrolysis process from a circular bioeconomy perspective. Corncob and wood residue have been selected as potential co-feed materials for co-pyrolysis with sewage sludge at three mixing ratios (25, 50, and 75 wt%). The functional unit (FU) for this study is 1000 kg of dried single or mixed feedstock. LCA results indicate that sewage sludge, in a singular pyrolysis scenario, demonstrated the most unfavorable outcome by causing a rise in all negative environmental indicators. In contrast, the overall environmental impacts are reduced by up to 48 %, when the sewage sludge is mixed with co-feed biomass (wood or corncobs), with corncob co-pyrolysis performing better than wood residue in most impact indicators. Energy recovery from a gas turbine provides significant benefits, generating about nine times of the required energy for gas turbine operation and supplying sufficient energy to sustain the whole process. This is notably evident for corncob co-pyrolysis, where the energy produced from gas recovery is equivalent to 59–181 % of energy requirement of the whole process and achieved the highest net positive energy balance (+1368 kWh/FU). Sensitivity analysis indicates that co-pyrolysis is more sensitive to bio-oil yield fluctuations and feedstock transportation. In conclusion, this study establishes that sewage sludge co-pyrolysis is a more environmentally friendly treatment approach when compared to single pyrolysis.

Numerical investigation on the wake and energy dissipation of tidal stream turbine with modified actuator line method

This study evaluates correction methods for the actuator line method in tidal stream turbine calculations. Findings indicate that three-dimensional Gaussian distribution coefficients align closely with experimental results when ε = 2dr. Tip loss correction addresses abnormal axial force coefficient elevation at the blade tip, while stall delay correction minimally impacts standard turbine operation. Root loss correction slightly affects the root vortex but notably delays the disappearance of the nacelle after tail flow's bimodal region to 4D, contrary to observations. Using a cylinder correction at the blade root improves the root vortex representation. Enhanced ALM, combined with LES, simulates wake and energy loss across varying turbulence intensities. At low turbulence, the spiral vortex structure is clearer, with fewer stray vortices and a more regular circular shape. Increasing turbulence blurs the structure, introducing more turbulent vortices and losing regularity. Entropy production concept represents energy losses as total, direct, and turbulence entropy production. Direct entropy production is minimal, localized at blade tip, nacelle, and support structures due to significant velocity gradients. Indirect entropy production causes substantial energy loss, resembling wake flow's vortex pattern due to turbulent pulsation. With higher turbulence, EPR, EPDD, and EPTD decline as wake vortices are disrupted, reducing energy loss.

Comparative evaluation of sand erosion in reversible turbine at pump mode and turbine mode

During the operation of reversible pump turbine, the flow passing components are often worn by sediments. In this paper, Euler-Euler computational fluid dynamics (CFD) method is used to simulate the liquid-solid two-phase steady flow in several pump modes and turbine modes. Finnie models are used to predict possible wear conditions and further analyze the causes of component wear. Results show that runner is the most easily worn component, which is related to local high flow velocity. The runner erosion position is mainly concentrated in the middle part of the pressure side. The erosion position of guide vane and stay vane is mainly concentrated in the leading edge and trailing edge, which depends on the change of condition. By daily weighted, the turbine mode is found has higher erosion rate than that of pump mode. This study provides the scientific support of anti-erosion of pumped storage units.

Hydrogen-Based Energy Systems: Current Technology Development Status, Opportunities and Challenges

The use of hydrogen as an energy carrier within the scope of the decarbonisation of the world’s energy production and utilisation is seen by many as an integral part of this endeavour. However, the discussion around hydrogen technologies often lacks some perspective on the currently available technologies, their Technology Readiness Level (TRL), scope of application, and important performance parameters, such as energy density or conversion efficiency. This makes it difficult for the policy makers and investors to evaluate the technologies that are most promising. The present study aims to provide help in this respect by assessing the available technologies in which hydrogen is used as an energy carrier, including its main challenges, needs and opportunities in a scenario in which fossil fuels still dominate global energy sources but in which renewables are expected to assume a progressively vital role in the future. The production of green hydrogen using water electrolysis technologies is described in detail. Various methods of hydrogen storage are referred, including underground storage, physical storage, and material-based storage. Hydrogen transportation technologies are examined, taking into account different storage methods, volume requirements, and transportation distances. Lastly, an assessment of well-known technologies for harnessing energy from hydrogen is undertaken, including gas turbines, reciprocating internal combustion engines, and fuel cells. It seems that the many of the technologies assessed have already achieved a satisfactory degree of development, such as several solutions for high-pressure hydrogen storage, while others still require some maturation, such as the still limited life and/or excessive cost of the various fuel cell technologies, or the suitable operation of gas turbines and reciprocating internal combustion engines operating with hydrogen. Costs below 200 USD/kWproduced, lives above 50 kh, and conversion efficiencies approaching 80% are being aimed at green hydrogen production or electricity production from hydrogen fuel cells. Nonetheless, notable advances have been achieved in these technologies in recent years. For instance, electrolysis with solid oxide cells may now sometimes reach up to 85% efficiency although with a life still in the range of 20 kh. Conversely, proton exchange membrane fuel cells (PEMFCs) working as electrolysers are able to sometimes achieve a life in the range of 80 kh with efficiencies up to 68%. Regarding electricity production from hydrogen, the maximum efficiencies are slightly lower (72% and 55%, respectively). The combination of the energy losses due to hydrogen production, compression, storage and electricity production yields overall efficiencies that could be as low as 25%, although smart applications, such as those that can use available process or waste heat, could substantially improve the overall energy efficiency figures. Despite the challenges, the foreseeable future seems to hold significant potential for hydrogen as a clean energy carrier, as the demand for hydrogen continues to grow, particularly in transportation, building heating, and power generation, new business prospects emerge. However, this should be done with careful regard to the fact that many of these technologies still need to increase their technological readiness level before they become viable options. For this, an emphasis needs to be put on research, innovation, and collaboration among industry, academia, and policymakers to unlock the full potential of hydrogen as an energy vector in the sustainable economy.

Comparison of Variable Speed Wind Turbine Control Strategies.

Variable speed operation of wind turbines presents certain advantages over constant speed operation. Basically, variable speed wind turbines use the high inertia of the rotating mechanical parts of the system as a flywheel; this helps to smooth power fluctuations and reduces the drive train mechanical stress. Also, variable speed systems could lead to maximise the capture of energy during partial load operation. In this paper alternative control strategies for variable speed operation are considered and compared from the point of view of energy yield and power quality. Control aim is always maximum power generation. Maximum power tracking and power fluctuation will be analysed when exciting the different configurations with a particular wind profile. Also fixed speed wind turbine are considered for the comparison.

A novel concept for a rib turbulator for optimizing the cooling performance in a square channel

In gas turbine operations, realizing the appropriate cooling of blades and vanes is crucial for ensuring long-term durability and high thermal efficiency. Internal convective cooling is widely used to direct coolant through a channel comprising rib turbulators to enhance the effectiveness of the cooling process. In this study, a numerical simulation is conducted to evaluate the effects of novel rib turbulator configurations under mist/steam two-phase conditions, specifically in relation to secondary flow and heat transfer characteristics. The morphologies of the secondary flow distribution and mist droplet trajectories induced by different rib turbulator configurations are carefully evaluated to elucidate the underlying mechanism of the heat transfer enhancement. Thus, the findings indicate that the configuration of the rib turbulator significantly affects the secondary flow distribution. In the novel concepts of discrete v-shaped rib turbulators with a single break and those with a double break, a notable increase in the longitudinal secondary flow was observed with a higher turbulence intensity. Moreover, such secondary flow compels mist droplets to accumulate and assemble at various locations within the channel. Subsequently, the heat transfer enhancement was localized in areas where the mist droplets accumulated in significant quantities. In terms of the optimization of the rib turbulator configuration, the adoption of a v-shape with a single break and discrete channel resulted in an enhancement of the Nusselt number by 45.07 % and the thermal performance factor by 88.57 %.